1. Field of The Invention
The present invention relates to a method for smoothing skip up-shifts in a vehicular automatic/semi-automatic mechanical transmission system, and in particular to a method for smoothing skip up-shifts in an automatic/semi-automatic mechanical transmission system which does not require an input signal indicative of the rotational speed of the engine.
2. Description of the Prior Art
Automatic and semi-automatic mechanical transmission systems for vehicles are well known in the prior art. Typically, such systems comprise a multi-speed mechanical change gear transmission, a master friction clutch drivingly interposed the engine and the transmission and a central processing unit or controller for receiving input signals from sensors and issuing command output signals to actuators for operation of the system according to predetermined logic rules. Systems of this type are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,081,065; 4,361,060; 4,595,986 and 4,648,290, the disclosures of which are hereby incorporated by reference.
Logic rules for allowing and/or commanding an automatic/semi-automatic transmission skip shift, i.e. a direct shift of more than one ratio step, are also known in the prior art as may be seen by reference to U.S. Pat. No. 4,576,065, the disclosure of which is hereby incorporated by reference.
To provide smooth re-engagement of the friction master clutch, especially after a dynamic skip up-shift, re-engagement should be commanded only when the speed differential between the driving friction member(s) (rotating at engine speed) and the driven friction member(s) (rotating at transmission input shaft speed) is no greater than a predetermined reference value. This is especially true for systems having input shaft decelerating means, such as input shaft brakes, wherein the engine will decelerate considerably less rapidly than the transmission inPut shaft during an upshift routine. In the automatic/semi-automatic mechanical transmission systems of the prior art, to achieve a smooth up-shift, especially for systems allowing/commanding skip up-shifts, a sensor for sensing engine speed with the clutch disengaged was required.